As concerns over maintaining proper health continue to grow, vitamin and antioxidant use and intake also continue to rise. As more evidence of the potential benefits associated with the use and intake of vitamins and antioxidants continues to be generated, demand for such substances increases, as does the demand for purer forms thereof. Many antioxidants and vitamins can be found in, and extracted from, natural sources. However, these natural sources, e.g., plants and vegetables, contain many undesirable components and impurities which are extracted along with the antioxidants.
Additionally, the incorporation of vitamins and antioxidants into more and more varied applications has generated further challenges. For example, consumers may prefer certain aesthetic qualities which make vitamins and antioxidants that are not color stable undesirable in certain formulations.
Tocopherol compounds are components of vegetable oils which exhibit vitamin E activity. Tocopherol compounds are found widely distributed in many organic substances, including grain oils and vegetable oils. However, the amount of tocopherol present in the natural oils may be small, and therefore, the oils are distilled to concentrate the tocopherol content. Unfortunately, the content of other undesirable co-boilers, as well as pesticides, fertilizers, etc. may also be concentrated. Moreover, the products are not necessarily color-stable.
As such, there have been many attempts to recover and purify antioxidants, such as tocopherols, from natural sources. For example, a method which involves mixing a tocopherol-containing material with a polar organic solvent and contacting this mixture with a strongly basic anionic exchange resin, whereby the tocopherols are absorbed onto the resin, and subsequently eluted with an acidic solution, has been described. However, such methods can result in resin fouling, and potential oxidation of the resins may result in a persistent amine odor. Moreover, resins are short-lived, expensive and provide relatively low capacity.
Other processes for the isolation of tocopherols involve treating deodorizer distillates, which comprise the “sludge” or distillate obtained in connection with the production of edible oils and fats subsequent to the deodorization step, with a lower aliphatic alcohol in the presence of an acid catalyst, often with prior saponification of the sludge, for the purposes of esterifying the free fatty acids present in the sludge. Other processes have been disclosed wherein the tocopherols and/or sterols are esterified with the free fatty acids contained in the distillates. However, these processes are often complicated, time-consuming and expensive. Moreover, most prior art processes for the purification or isolation of tocopherols and/or sterols which involve the esterification of the tocopherols and/or sterols with free fatty acids present in the feed are incapable of adequately removing impurities and other components which co-distill with tocopherols and/or sterols, at sufficient yields.
Another process for the separation of tocopherols has been described wherein borate esters are formed, the mixture is distilled and the esters are subsequently hydrolyzed, with subsequent separation of the borate source from the tocopherol. While such a process generally removes a large portion of the impurities that co-distill with the tocopherol, significant amounts of the tocopherol in the original feed material can be lost during the purification, foaming during the esterification process is a significant problem, and undesirable borate solids can form requiring additional separation steps.
Other processes which may result in acceptable levels of certain impurities do not meet all currently desired purity specifications, and moreover, fail to provide color stability characteristics which are satisfactory in all applications.
Thus, there is a need in the art for a process by which tocopherol compounds can be purified in high yield from natural sources to provide color-stable tocopherol compositions.